Anaesthetics administering apparatus



April 15, 1969 R SUGG ET AL. 3,438,372

ANAESTHETICS ADMINISTERING APPARATUS Filed Dec. 2. 1966 Sheet of 3 I A o5 O O 4/ I x 37 l -y/ 23 f7 .47

nwE/vmes Ens/L fiqmo vo 50 5 A iil 15, 1969 B. R. SUGG ET AL 3,438372ANAESTHETICS ADMINISTERING APPARATUS Filed Dec. 2, 1966 Sheet of 3 l.. ymlvs/vroes 545/4 R4 man 0 5066 JOHN LLOYD Arm/mars April 15, 1969 B. R.sues ET AL 3,438,372

ANAESTHETICS ADMINISTERING APPARATUS Filed Dec. 2, 1966 Sheet 3 of 5 I72 6/ gym a1 @J O 50a L4 UN .59 \An 70 '1 BASIL RAW $2 35;

4/ JOHN 110m United States Patent 3 438,372 ANAESTHETICS ADMINISTERINGAPPARATUS Basil R. Sugg, Abingdon, and John Lloyd, Oxford, England,assignors to Longworth Scientific Instrument Company Limited, Abingdon,England, a British coman p y Filed Dec. 2, 1966, Ser. No. 598,680 Claimspriority, application Great Britain, Dec. 10, 1965, 52,580/ 65 Int. Cl.A61m 17/00, 15/00; B01d 47/16 U.S. Cl. 128---188 17 Claims ABSTRACT OFTHE DISCLOSURE An anaesthetic administering apparatus having avapourising chamber through which a carrier gas is passed to entrainanaesthetic vapour, the flow of the carrier gas being controlled by asingle valve having three positions, these being an off position inwhich the carrier gas is passed directly to the patient without passingthrough the vapourising chamber and in which position anaesthetic cannotbe introduced into the chamber, a fill position in which the carrier gasis again passed directly to the patient but in which anaesthetic can beintroduced mto the vapourising chamber, and an on position in which thecarrier gas passes through the vapourising chamber before reaching thepatient and in which, once again, anaesthetic cannot be introduced intothe chamber.

This invention relates to apparatus for administering anaesthetics, andis particularly directed to the provision of an improved control valvefor such apparatus.

The kind of apparatus with which the invention is concerned is that inwhich a carrier gas for anaesthetic vapour is led in operation to abreathing mask for a patient via a vapourising chamber charged withliquid anaesthetic whose vapour is entrained by the carrier gas in itspassage through such chamber. The carrier gas may be air or oxygen, forexample, and it may either be breathed in and out by the patient underhis own volition or, alternatively, supplied under elevated pressure sothat no assistance from the patient is required.

When it becomes necessary to recharge the vapourising chamber withanaesthetic liquid during the operation of such apparatus, as willsometimes occur, it is important the flow of carrier gas through thechamber should be cut off during such recharging as otherwise thepatient may temporarily receive an undesirably high concentration ofanaesthetic; also, when the carrier gas is pressurised, it may blow partof the new charge of liquid anaesthetic out of the vapourising chambertowards the patient if its flow through such chamber is not so arrested.Furthermore, the presence of pressurised carrier gas in the chamber mayprevent the entry of a new liquid charge altogether.

In known apparatus such cutting off of the flow of carrier gas throughthe vapourising chamber can only be achieved either at the expense ofalso cutting off the flow of the gas direct to the patient (i.e. not viathe vapourising chamber) which may be very undesirable or, in order tomaintain the latter flow, by operating a number of sepa- "ice ratecontrols in a correct manner and sequence. It is a primary object of thepresent invention to provide means whereby these difficulties may beovercome or considerably reduced.

Thus, according to the invention there is provided apparatus foradministering anaesthetics, such apparatus including an inlet for ananaesthetic carrier gas such as air or oxygen, an outlet connectib le toa breathing mask for a patient, a vapourising chamber adapted to hold acharge of a liquid anaesthetic, and a valve for controlling both thepath of flow of said carrier gas through the apparatus and the entry ofliquid anaesthetic into the vapourising chamber to charge the same, acontrol member of such valve being adjustable to any one of threepositions these being a first position in which, in operation, the saidcarrier gas is directed to flow from said inlet to said outlet withoutpassing through the vapourising chamber and charging passage to suchchamber is closed, a second position in which, in operation, the saidcarrier gas is directed to flow from said inlet to said outlet withoutpassing through the vapourising chamber and said charging passage isopen, and a third position in which, in operation, the said carrier gasis directed to flow from said inlet to said outlet via the vapourisingchamber and said charging passage is closed.

The said first position of the valve control member, hereinafterreferred to as the off position, is thus one in which the vapourisingchamber is sealed so that anaesthetic vapour cannot escape therefromeither to a patient or or atmosphere, but in which a passage for theflow of carrier gas from the inlet to the outlet is neverthelessprovided so that a patient will still be able to breathe by way of suchpassage if a breathing mask connected to the outlet is applied to hisface with the apparatus in its off condition.

With the valve control member in its said second position, hereinafterreferred to as the fill position, the or each charging passage to thevapourising chamber is open to permit the chamber to be charged withliquid anaesthetic; means will of course be provided to permit theegress from the chamber of gas displaced by such liquid. As previouslymentioned it is important that the carrier gas supplied to the patientshould not be permitted to flow through the vapourising chamber duringsuch filling step, and this desideratum is achieved in the apparatusaccording to the invention; nevertheless the flow of carrier gasdirectly to the patient without its passing through the vapourisingchamber is still permitted so that the patient can continue to receivethe full flow of carrier gas during a recharging operation.

In the third position of the valve control member, hereinafter referredto as the on position, the carrier gas is led from the inlet through thevapourising chamber and thence to the outlet to the patient, the or eachcharging passage being closed. This is thus the operative condition ofthe apparatus.

In a preferred form of the invention the said valve control memberincludes a rotary cock formed to define the various passages for settingup the appropriate communications between the inlet and outlet and thevapourising chamber of the apparatus in the three conditions of thecontrol valve referred to above. In such preferred embodiment the saidvalve cock is rotatably mounted in a seating formed with a number ofpassages for the flow of carrier gas, liquid anaesthetic and a mixtureof carrier gas and anaesthetic vapour as the case may be; all of thesepassages open into the heating surface for the valve and such passagesare:

(a) One leading from the said inlet of the apparatus for the passage ofpure carrier gas;

(b) One leading to the said outlet of the apparatus;

One leading to the vapourising chamber for the flow of pure carrier gasthereinto;

(d) One leading from the vapourising chamber for the flow of carrier gasand entrained anaesthetic vapour therefrom;

(e) One leading from the vapourising chamber for the flow to the valveof air displaced from such chamber by a new charge of anaestheticliquid;

(f) One leading to the outside atmosphere for the passage of suchdisplaced air; and

(g) One leading to the vapourising chamber for the passage ofanaesthetic liquid thereto during charging.

The valve cock itself is, in such preferred embodiment, formed with apassage (h) into which anaesthetic liquid may be introduced when thevapourising chamber is to be charged, such passage having an outlet intothe seating surface of the cock.

The valve cock of such preferred embodiment is so formed that in itssaid olf position it provides a communication only between passages (a)and (b); in its fill position it provides communications only betweenpassages (a) and (b), between passages (e) and (f), and between passages(h) and (g); in its on position it provides communications only betweenpassages (a) and (c) and between passages (d) and (b).

It will be understood from the above that the only communication whichhas to be effected in more than one position of the valve cock is thatbetween passages (a) and (b) in both the off and fill positions. Clearlythis effect may be achieved by providing two separate bores through thevalve cock, for example, or in various other ways; in a preferredconstruction a communicating channel is formed in the valve cock betweencircumferential channels in its seating surface which circumferentialchannels communicate one with each of the passages (a) and (b) in boththe off and fill positions of the valve cock. This preferredconstruction was the advantage that a connection between passages (a)and (b) is provided at all intermediate positions of the cock, so thatthe supply of carrier gas to the patient cannot be cut off byinadvertent movement of the cock during use.

Clearly the cock could be formed with various different arrangements ofbores therethrough and channels in its seating surface to set up thedesired communications in its respective positions of rotation. In apreferred form the communications between passages (a) and (c), and (d)and (b), respectively, in the on position of the valve cock are bothprovided by channels formed in the seating surface of the cock, whilstthe communication between passages (e) and (f) in the fil-l position isformed by a bore.

In a preferred form of the invention, access to the passage (h) in thevalve cock for the delivery of anaesthetic liquid thereinto when thevapourising chamber is to be charged is provided through one or moreapertures leading into such passage from an exposed surface of the valvecock. In a particularly convenient arrangement such exposed surface ofthe cock is constituted by a top horizontal surface thereof in thenormal position of use of the apparatus, iWhiCh surface is arranged atthe bottom of a dished top surface portion of the part of the apparatusdefining the said seating, into which a dose of liquid anaesthetic canbe poured so as to run into the passage (h) in the cock by way of suchaperture or apertures. Such passage in the valve cock could, if desired,be re- 4 placed by a bore therethrough to provide, in the fill positionof the cock, a communication to the passage (g) from a further passagein the seating into which latter passage a dose of liquid anaestheticcould be introduced in some other manner.

In a preferred form of the invention, in which the valve control membercomprises a rotary cock, the three aforementioned positions of thelatter are arranged at to one another in the rotation of the cock aboutits axis. A manually operable handle will generally be provided forrotating the valve member between its said positions, together withmeans for clearly indicating the location of such positions.

The apparatus according to the invention preferably includes aproportioning valve for controlling the concentration of anaestheticvapour in the gaseous mixture delivered to the patient in the onposition of the apparatus and, in accordance with an important preferredfeature of the invention, such proportioning valve is located within thevapourising chamber and close to but above what will be the maximumlevel of the anaesthetic liquid in operation. Such location of theproportioning valve helps to ensure that the concentration ofanaesthetic vapour in the gaseous mixture delivered to a patient will beconsistent for varying rates of flow of the carrier gas.

The proportioning valve may, as in a preferred form of the invention,include a double tapered valve member arranged to be infinitelyadjustable between one extreme position in which, in operation, all ofthe carrier gas which it directs from the vapourising chamber to thesaid outlet has passed through the anaesthetic vapour in the vapourisingchamber and another extreme position in which none of the carrier gasdelivered to the outlet by way of such proportioning valve has entrainedany anaesthetic vapour in the vapourising chamber and another extremeposition in which none of the carrier gas delivered to the outlet by wayof such proportioning valve has entrained any anaesthetic vapour.Clearly the concentration of anaesthetic vapour in the gaseous mixturedelivered to a patient may be varied between these two extremes. Anyconvenient kind of proportioning valve may be employed in the apparatus,e.g. a rotary valve member could be used instead of the double taperedvalve member referred to above.

Means will, of course, be provided for adjusting such proportioningvalve and may take any of a variety of forms; obviously a rotary valvecould be adjusted by way of a rotary shaft accessible outside of thevapourisilng chamber. In a preferred embodiment in which the valvemember is of the double tapered variety such member is mounted on anaxially adjustable shaft movable by cam means.

As the volatility of the anaesthetic liquid in the vaporising chamber,and thus the concentration if its vapour, will vary with ambienttemperature, means are preferably provided in association with the saidproportioning valve for compensating for such variations. In a preferredembodiment such means comprises a subsidiary valve adapted, inoperation, to control the flow of that proportion of the carrier gaswhich has been passed through the anaesthetic vapour, such subsidiaryvalve being itself controlled by a sealed temperature-responsivecapsule.

The vapourising chamber of the apparatus will preferably house one ormore wicks, formed for example of brushed nylon, for soaking up theanaesthetic liquid and thus causing its vapour to be distributedthroughout the chamber in operation. Preferably two tubular wicks areprovided and are arranged concentrically of one another to define atubular passage for the flow of carrier gas through the anaestheticvapour.

Means are preferably provided for reducing temperature fluctuations inthe apparatus by increasing its thermal mass, and may conveniently takethe form of a water jacket whose top wall forms the base of thevapourising chamber.

The seating for the control valve of the apparatus may conveniently takethe form of a metal block forming the lid of the vapourising chamber; ina preferred form of the invention the passages for the flow of carriergas between the aforementioned passages (c) and (d) in said seatingmember and the proportioning valve of the apparatus take the form offlexible tubes formed of a suitable synthetic plastics material.

In order that the invention may be more readily understood, oneembodiment of the same will now be described by way of example and withreference to the drawings accompanying the provisional specification inwhich:

FIGURE 1 is a vertical medial cross-section through the apparatus;

FIGURE 2 is a top plan view of the apparatus with the adjusting handleof its control valve removed for the sake of clarity;

FIGURE 3 is a vertical cross-section of the top part of the apparatus,taken on the line III-III of FIG. 2 but with the control valve adjustinghandle in position;

FIGURE 4 is a vertical cross-section of the top part of the apparatus,taken on the line IV-IV of FIG. 2, again with the control valveadjusting handle in position;

FIGURE 5 is a view in side elevation of the control member of thecontrol valve of the apparatus;

FIGURES 6- to are cross-sections on the lines VI to X respectively ofFIG. 5; and

FIGURES 11 to 13 are diagrammatic illustrations of the various flowsthrough the control valve in the said off, fill, and on positionsthereof, respectively.

Referring first to FIGS. 1 to 4, the illustrated apparatus comprises twobasic parts, i.e. a vapourising chamber 1 and a head 2 which headcarries the control valve of the apparatus, such control valve beinggenerally indicated at 3.

The side wall of the vapourising chamber 1 is constituted by a metaltube 4 of square cross-section, whilst the bottom of such chamber isformed by the top wall of a water jacket 5 secured in the bottom of thetube 4; the roof of the chamber is formed by the head 2.

Housed within the vapourising chamber 1 is a proportioning valveassembly generally indicated by 6, a temperature'responsive valvegenerally indicated by 7, and a pair of brushed nylon wicks 8 and 9 ofsquare cross-section which together define a tubular space 10 closed atits lower end by the int-urned end of the outer wick 9.

Referring now particularly to the proportioning valve assembly 6(FIG. 1) this comprises an open-ended tubular housing 11 formed with aninlet opening 12 by way of which carrier gas such as air or oxygen isreceived from the control valve 3, and an outlet opening 13 throughwhich a gaseous mixture containing a concentration of anaesthetic vapourdetermined by the setting of the proportioning valve is transmitted backto the control valve for delivery to a patient.

The main tubular housing 11 of the proportioning valve contains fiveflow control members 14 to 18 which are maintained in position by theengagement of an externally screw-threaded flange 19 of the lowestmember 18 with an internally screw-threaded sleeve 20 at the bottom ofthe housing 11.

A control shaft 21 of the proportioning valve extends vertically andcentrally thereof and is engaged at its top end by an eccentricallymounted circular cam member 22 controlled by means referred tohereinafter. The control shaft is biased upwardly by a compressionspring 23 bearing between a nut 24 thereon and the closed top of thehousing 11 and is thus movable up and down under the influence of thespring 23 and the cam 22. The control shaft carries a double taperedvalve member 25 cooperating with seatings defined by the bounding edgesof central apertures 26 and 27 in the flow control members 15 and 17respectively.

It will be observed that the flow control members 14 and 15 enclosed aspace 28 which communicates, via openings 29 in the wall of the member14 and passages 30 in the wall of the housing 11, with the exterior ofsuch housing; such space 28 is also in communication with the inlet 12to the housing via circular opening 31 in flow control member '14. Alsothe space 32 defined within the flow control members 15, 16 and 17communicates with the outlet 13 from the housing via openings 33 in thewall of the member 16, whilst the space 34 between the flow controlmembers 17 and 18 communicates with the exterior of the housing 11 viabores 35 in the member 18.

The space within the inner wick 8 is divided into upper and lower partsby a square plate 36 which supports the proportioning valve assembly andis itself supported at its corners by four pillars 37 secured to a topmounting plate 38 beneath the head 2.

The whole proportioning valve assembly is enclosed by a square-sectionedtubular casing 39 which makes a sliding fit thereon and is formed withan opening 40 in each side wall thereof near to its lower end; the innerwick 8 is a close fit over such casing 39.

The path of carrier gas through the vapourising chamber and theproportioning valve is as follows. Gas entering the proportioning valveassembly at 12 from the control valve 3 passes through opening 31 intothe space 28 from whence it can pass through openings 29 and apertures30 and then over the top of the inner wick 8 into the space 10 betweenthe two wicks. The carrier gas can then flow through the inner wick 8and the openings 40 in the casing 39, through the bores 35 in the flowcontrol member 18, and thus into the space 34. In the course of its flowbetween the apertures 30 and the space 34 the carrier gas will entrainanaesthetic vapour.

It will thus be seen that, in operation, there will always be a supplyof pure carrier gas to the space 28 immediately above the double taperedvalve member 25 and a supply of carrier gas carrying anaesthetic vapourto the space 34 immediately below the valve member. The proportions ofanaesthetic-free carrier gas and anaesthetic-impregnated carrier gas inthe gaseous mixture supplied to the outlet 13 from the proportioningvalve will thus clearly depend on the position of the valve member 25relative to its upper and lower seating surfaces. In the illustratedcondition of the apparatus the valve member is in its fully depressedposition in. which the opening 27 in the flow control member 17 iscompletely sealed thereby, so that no anaesthetic-impregnated carriergas can flow into the space 32 and thence to the outlet 13; onlyanaesthetic-free carrier gas can thus fiow to the outlet by way ofopening 26 in flow control member 15. Obviously in the other extremeposition of the valve member 25 only anaesthetic-impregnated carrier gaswill flow to the outlet, the opening 26 being completely sealed.Infinite adjustment of the valve member between these two extremes isclearly possible.

Rotation of the cam 22 to adjust the position of shaft 21 and thus valvemember 25 is effected by means of knob 41 (FIG. 4) via shaft 42 on whichthe circular cam is eccentrically mounted. The knob 41 carries a pointerand is surrounded by a scale 43 for indicating the concentration ofanaesthetic which will be delivered in the various positions of thevalve member 25.

The temperature-responsive valve 7 already referred to comprises a valvemember 44 slidably mounted on the bottom of the shaft 21 and biaseddownwardly by a compression spring 45 mounted in an axial bore in suchshaft. An annular shoulder 46 on the valve member 44 is movablerelatively to a seating surface defined by an annular ridge 47 on theflow control member 18 so as to control the flow ofanaesthetic-impregnated carrier gas into the space 34 via the bores 35in such flow control member.

The valve member 44 is secured to a sealed temperaturesensitive capsule48 fixedly mounted above a bottom plate 49 suspended from the pillars37, the capsule 48 being immersed in the anaesthetic liquid inoperation. The maximum level of such liquidis indicated at 50.

It will be clear that an increase or decrease in the temperature of theanaesthetic liquid, and a consequent rise or fall in its volatility andthe concentration of its vapour, will bring about a correspondingexpansion or contraction of the capsule 48 to raise or lower the valvemember 44 and thus enlarge or restrict the annular flow space for theanaesthetic-impregnated carrier gas defined between the shoulder 46 ofthe valve member and its seating surface 47.

Referring now to the construction of the head 2 of the apparatus,housing the control valve 3-, such head is a heavy metal casting formedat its rear part with bores 51 and 52 in which are screw-threadedlymounted the main inlet and outlet members 53 and 54 of the apparatus.The inlet member 53 will be connected in operation to a source ofcarrier gas whilst the outlet member 54 will be connected to a breathingmask for a patient. The head is also formed with a dished portion 55 inits top surface, and a conical bore 56 which forms a seating for aconical control cock 57 of the control valve 3. The control cock isfurnished with a handle 58 by means of which it may be rotated in itsseating 56.

The head is formed with a bore 59 (FIG. 3) leading from the inlet 53 andopening into the conical seating 56 of the control cock, and a bore 60opening from such seating and leading to the outlet 54. Further bores 61and 62 lead from such seating to the underside of the head and areconnected via flexible pipes 63 and 64 respectively to the inlet 12 andoutlet 13 of the proportioning valve.

A further bore 65, not visible in FIG. 3 but illustrateddiagrammatically in FIGS. 11 to 13, leads from the seating 56 and isconnected by a flexible pipe 66 to the upper end of one of the pillars37 which is of hollow construction and has an outlet 67 therefrom nearto the bottom of the vapourising chamber. A bore 68, again not visiblein FIG. 3 but illustrated diagrammatically in FIGS. 11 to 13, leads fromthe seating 56 and is connected by a flexible pipe 69 to another one ofthe pillars 37 which is also of hollow construction and has an inlet 70thereto.

One further bore 71, narrower than those already mentioned, is providedin the head 2 and connects the conical seating 56 with the outsideatmosphere via an opening in the side of the head casting. Such bore isagain indicated diagrammatically in FIGS. 11 to 13.

The conical control cock is formed to provide the appropriateinterconnections between the above-described bores in the head 2 in theoff, fill, and on positions of the control valve, and its constructionis illustrated in FIG. 3 and FIGS. to 10.

Thus the control cock is formed with a bore 72 extending completelytherethrough and arranged at an obtuse angle to the axis of rotation ofthe cock, and with two horizontal circumferential channels 73 and 74into which the ends of the bore 72 opens; alternatively, if desired, thechannels 73 and 74 could be interconnected by a further channelextending at right angles to them in the cock surface, and the bore 72omitted. In the aforementioned ofl position of the control valve,illustrated diagrammatically in FIG. 11, the bore 59 in the head isconnected to the bore 60 therein by way of channel 73, bore 72 andchannel 74 in the control cock. All of the other bores in the head areblocked by the control cock. Thus, in the off position of the controlvalve, carrier gas entering the apparatus at inlet 53 simply passesstraight through the control valve to outlet 54; such flow is indicatedin FIG. 11.

The control cock is also formed with a narrow diameter bore 75 extendingcompletely therethrough and with a blind bore 76 which is aligned withthe top horizontal surface of the cock and connected with such surfaceby apertures 77. When the control cock is rotated through 90 in theanticlockwise sense as seen from above, its off position illustrated inFIG. 11 to its fill position illustrated in FIG. 12, the narrow bore 75will come into such a position as to connect bore 68 in the head withbore 71 therein, whilst the open end of blind bore 76 will be broughtinto alignment with bore 65 in the head. The channels 73 and 74 in thecock ensure that the bores 59 and 60 in the head are stillinterconnected by way of the bore 72 in the cock.

Thus, in such fill position of the control valve, communication isprovided firstly between the apertures 77 in the top surface of thecontrol cock and the inlet 67 at the bottom of the vapourising chamberso that a dose of anaesthetic liquid poured into the dished portion 55of the head will run down into the vapourising chamber by way ofapertures 77, blind bore 76, bore 65, flexible pipe 66, pillar 37 andinlet 67; secondly between outlets from the vapourising chamber and bore71 in the head so that air can be displaced from the vapourising chambervia outlet 70, pillar 37, flexible pipe 69, and bores 68, and 71; andthirdly between the bores 59 and 60 in the head so that carrier gas canstill pass directly to a patient as in the off position of theapparatus. Thus, when the control cock is in its fill position thevapoursizing chamber can be re-charged with anesthetic liquid withoutthe flow of carrier gas to the patient being cut off, although suchcarrier gas will not have passed through the vapourising chamber forreasons explained hereinbefore. The flows in this position of the cockare indicated in FIG. 12.

The position of air outlet 70 from the vapourising chamber defines themaximum liquid level 50 as no more liquid can enter the chamber oncesuch air outlet has been covered thereby.

Further rotation of the control cock through 90 will bring it into itson position illustrated in FIG. 13. In this position the bore 59 in thehead is put in communication with the bore 61 therein by way of avertical channel 78 in the surface of the control cock, whilst the bores62 and 60 are similarly interconnected by a channel 79. The bore 59 isthus connected to the inlet 12 of the proportioning valve via channel78, bore 61 and flexible pipe 63, whilst the outlet 13 from theproportioning valve is connected to bore 60 via flexible pipe 64, bore62 and channel 79. Carrier gas delivered to the inlet 53 of theapparatus will therefore pass to the proportioning valve and some or allof such gas will be passed through the vapourising chamber in the manneralready described, and thereafter delivered to a patient via outlet 54.This is, of course, the normal operational condition of the apparatus.The flow in this position of the cock is indicated in FIG. 13.

The channels 73 and 74 extend round the circumference of the valve cockto an extent such that at any position thereof from the off position toa point close to the on position there is always free passage forcarrier gas from the bore 59 to the bore 60. The widths of the websbetween the adjacent ends of channels 73 and 78 and the adjacent ends ofchannels 74 and 79 are less than the width of bores 59 and 60, so that apassage for the flow of carrier gas through the vapourising chamber viachannels 78 and 79 is opened before the communication between bores 59and 60 is closed. Thus there is no position of the cock in which thesupply of carrier gas to the patient is obstructed.

The position of the control cock at any particular time is indicated bylettering on its handle 58' illustrated in the drawings and alwaysvisible from the front of the apparatus. The mode of engagement betweenthe handle 58 and a mounting stub 80 therefor on the top of the controlcock is such that the handle cannot be placed on the cock in any but theposition in which it correctly indicates the position of the cock.

It will-thus be seen that the invention provides apparatus fordelivering anaesthetic which whilst being highly versatile isnevertheless extremely simple to operate. Control of the flow throughthe apparatus by means of a single operating handle has the importantadvantage that it is impossible to carry out two or more controloperations in the wrong sequence or to omit to perform one of them atall, as may well occur with known apparatus in which the flow of carriergas and anaesthetic liquid is controlled by more than one valve or othercontrol element.

We claim:

1. Apparatus for administering anaesthetics, such apparatus including aninlet for an anaesthetic carrier gas such as air or oxygen, an outletconnectible to a breathing mask for a patient, a vapourising chamberadapted to hold a charge of a liquid anaesthetic, at least one chargingpassage to said chamber, a valve for controlling both the path of flowof said carrier gas through the apparatus and the entry of liquidanaesthetic into the vapourising chamber to charge the same, and acontrol member for said valve, said control member being adjustable toany one of three positions these being a first position in which, inoperation, the said carrier gas is directed to flow from said inlet tosaid outlet without passing through the vapourising chamber and saidcharging passage to said chamber is closed, a second position in which,in operation, the said carrier gas is directed to flow from said inletto said outlet without passing through the vapourising chamber and saidcharging passage is open, and a third position in which, in operation,the said carrier gas is directed to flow from said inlet to said outletvia the vapourising chamber and said charging passage is closed.

2. Apparatus as claimed in claim 1, wherein the said valve controlmember comprises a rotary cock formed to define passages for setting upthe appropriate communications between the inlet and outlet and thevapourising chamber of the apparatus in the three said positions of saidcontrol member.

3. Apparatus as claimed in claim 2, wherein the arrangement is such thata passage for the flow of carrier gas from the said inlet to the saidoutlet is also provided when the said valve cock is in any position ofadjustment other than the said first, second and third positionsthereof.

4. Apparatus as claimed in claim 2, including a seating in said valve,said valve cock being rotatably mounted in said seating, passages formedin said seating which passages open into the seat surface thereof andwhich passages comprise:

(a) one leading from the said inlet of the apparatus for the passage ofpure carrier gas;

(b) one leading to the said outlet of the apparatus;

() one leading to the said vapourising chamber for the flow of purecarrier gas thereinto;

((1) one leading from the vapourising chamber for the flow of carriergas and entrained anaesthetic vapour therefrom;

(e) one leading from the vapourising chamber for the flow to the valveof air displaced from such chamber by a new charge of anaestheticliquid;

(f) one leading to the outside atmosphere for the passage of suchdisplaced air; and

(g) one constituting a charging passage and leading to the vapourisingchamber for the passage of anaesthetic liquid thereto during charging;the said valve cock being formed with a passage (h) into whichanaesthetic liquid may be introduced when the vapourising chamber is tobe charged, such passage having an outlet into the said seating surfacefor the cock; and the valve cock being so formed that when in its saidfirst position it provides a communication only between passages (a) and(b), when in its said second position it provides communications onlybetween passages (a) and (b) between passages (e) and (f) and betweenpassages (h) and (g), and when in its said third position it providescommunications only between passages (a) and (c) and between passages(d) and (b).

5. Apparatus as claimed in claim 4, including two circumferentialchannels formed in the seating surface of said valve cock, whichcircumferential channels communicate one with each of the passages (a)and (b) in both the first and second positions of the cock, suchcircumferential channels being interconnected by a further channel orbore to provide the communication between passages (a) and (b) in thesaid first and second positions of the cock.

6. Apparatus as claimed in claim 5, including respective channels formedin the seating surface of the valve cock to provide the communicationsbetween passages (a) and (c) and between passages (d) and (b) in thesaid third position of the cock.

7. Apparatus as claimed in claim 4, including a bore formed in the saidvalve cock to provide the communication between passages (e) and (f) inthe said second position of the cock.

8. Apparatus as claimed in claim 4, including one or more aperturesleading into the passage (h) in the valve cock from an exposed surfaceof the said cock to provide access to said passage (h) for the deliveryof anaesthetic liquid thereinto when the vapourising chamber is to becharged.

9. Apparatus as claimed in claim 8, wherein the part of the apparatuswhich defines the said seating for the valve cock is formed with adished top surface portion into which a dose of liquid anaesthetic canbe poured, and the said exposed surface of the valve cock is a tophorizontal surface thereof which is arranged at the bottom of saiddished surface so that a dose of liquid anaesthetic poured into saiddished surface may run into the passage (h) in the valve cock by Way ofsaid aperture or apertures.

10. Apparatus as claimed in claim 4, including a metal block forming thelid of the said vapourising chamber, the seat seating for the valve cockbeing formed in said metal block.

11. Apparatus as claimed in claim 4, wherein the three said positions ofthe rotary valve cock are arranged at to one another in the rotation ofthe cock about its axis.

12. Apparatus as claimed in claim 1, including a proportioning valve forcontrolling the concentration of anaesthetic vapour in the gaseousmixture delivered by the apparatus when the said control member thereofis in its said third position, such proportioning valve being locatedwithin the vapourising chamber and close to but above what will be themaximum level of the anaesthetic liquid in operation.

13. Apparatus as claimed in claim 12, wherein the said proportioningvalve includes a double tapered valve member arranged to be infinitelyadjustable between one extreme position in which, in operation, all ofthe carrier gas which it directs from the vapourising chamber to thesaid outlet has passed through the anaesthetic vapour in the vapourisingchamber and another extreme position in which none of the carrier gasdelivered to the outlet by way of such proportioning valve has entrainedany anaesthetic vapour.

14. Apparatus as claimed in claim 13, including an axially adjustableshaft mounting the said valve member of the proportioning valve, and cammeans for adjusting said shaft. perature responsive means associatedwith the said pro- 15. Apparatus as claimed in claim 12, includingtemportioning valve and adapted, in use of the apparatus, to influencethe operation of the latter in such manner as to compensate for theeffect of ambient temperature variations on the volatility ofanaesthetic liquid in the vapourising chamber.

16. Apparatus as claimed in claim 15, wherein the said temperatureresponsive means comprises a subsidiary valve adapted, in operation, tocontrol the flow of that proportion of the carrier gas which has beenpassed through the anaesthetic vapour, and a sealed temperatureresponsive capsule controlling such subsidiary valve.

17. Apparatus as claimed in claim 1, including a Water jacket whose topwall forms the base of the said vapourising chamber.

1 2 References Cited L. W. TRAPP, Primary Examiner.

US Cl. X.R.

